Such a punching tool with releasable locking against axial relative movements between the punching die and the die plunger is known from French Patent No. 2 641 486 A1. There, three screws acting as holding elements, which are radially screwed into corresponding transverse threaded bores in the die plunger, engage with rounded, hardened ends an annular groove in the shaft of the punching die. The screws fix the punching die axially on the die plunger and absorb the forces occurring on the punching die in the course of the punching stroke, as well as during the return stroke, and transfer them to the die plunger. Since in this case the stressed surfaces are very small, the known punching tool cannot absorb large punching forces. Moreover, changing of the punching tool is very awkward, since several screws must be removed and screwed back in again to accomplish this.
Furthermore, punching tools with releasable locking against relative rotating movements between the punching die and the die plunger are known from U.S. Pat. Nos. 2,172,272 and 5,131,303. Such locking to prevent movements in both directions of rotation is necessary because the punching die is connected with the die plunger by a screw thread, which transmits the axial loads occurring during punching from the punching die to the die plunger and permits a compensation of the total length of the punching die and the die plunger after re-grinding. To prevent a relative rotating movement of the two threaded elements, and therefore a change of the total length, the exterior thread is cut by several axial longitudinal grooves distributed over the circumference, and a pointed pin, seated in a transverse bore of the screw thread element with the interior screw thread, is pushed into one of the longitudinal grooves by a spring washer. In U.S. Pat. No. 5,131,303, the pointed pin is embodied as one piece with a spring washer and is prevented from a radial backing movement out of the longitudinal groove in that the bore wall of the guide bushing blocks a widening of the spring washer. Basically the locking must absorb the loads in both directions of rotation. If the spring washer is outside of the bore in the guide bushing, a relative rotation of the screw thread elements is possible, wherein it is necessary for releasing and renewed connecting of the punching die with the die plunger to overcome the rotary locking several times in the course of each revolution.